This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This phase II SBIR application will continue the development of an inexpensive point-of-care card/reader system for monitoring CD4+ cells in HIV-infected subjects, for use in resource poor areas. The technology uses a thin-film laminated microfluidic cassette to collect, count and store the blood sample while the required detecting reagents are stored and injected into the cassettes from the bench top unit. The aims are designed to systematically develop and troubleshoot the device, ultimately validating its readings comparing with standard flow cytometry using whole blood from human subjects to enumerate CD4+ cells in small volumes for less than $1.50 per test. We have shown that fluorescent beads of a specific size coated with antibody can specifically label human CD4 cells (both monocytes and T cells) and that these cells are detected and discriminated in the cassette, as well as in the standard flow cytometer.